348 Marsh — Restorations of Olaosaurus and Ceratosanrus. 



The lower jaws of Ceratosanrus are large and powerful, 

 especially in the posterior part. In front, the rami are much 

 compressed, and the}' were joined together by cartilage only. 

 There were fifteen teeth in each ramus, similar in form to 

 those of the upper jaws. 



The cervical vertebrae of Ceratosaurus differ in type from 

 those in any other known reptiles. With the exception of the 

 atlas, all are strongly opisthocoelian, the cup on the posterior 

 end of each centrum being unusually deep. In place of an 

 equally developed ball on the anterior end, there is a perfectly 

 flat surface. The size of the latter is such that it can only be 

 inserted a short distance in the adjoining cup. This peculiar 

 articulation leaves more than three-fourths of the cup unoccu- 

 pied by the succeeding vertebra, forming, apparently, a weak 

 joint. 



The dorsal and lumbar vertebrae are bi-concave, with only 

 moderate concavities. The sides and lower surface of the 

 centra are deeply excavated, except at the ends. All the pre- 

 sacral vertebrae are very hollow, and this is also true of the 

 anterior caudals. 



There are five well coossin'ed vertebrae in the sacrum of the 

 present specimen of Ceratosaurus nasicornis. The transverse 

 processes are very short, each supported by two vertebrae, and 

 they do not meet at their distal ends. The caudal vertebrae 

 are bi-concave. All the anterior caudals, except the first, sup- 

 ported very long chevrons, indicating a high, thin tail, well 

 adapted to swimming. The tail was quite long, and the distal 

 caudals were very short. 



The scapular arch of Ceratosaurus is of moderate size, but 

 the fore limbs are very small. The humerus is short, with a 

 strong radial crest. The radius and ulna are also very short, 

 and nearly equal in size. The carpal bones were only imper- 

 fectly ossified. There were four digits in the fore foot, and 

 all were armed with sharp claws. The second and third digits 

 were much larger than the first and fourth, and the fifth was 

 entirely wanting. 



The pelvic arch of Ceratosaurus is of special interest. In 

 the type specimen here restored, the ilium, ischium, and pubis, 

 on each side, are firmly coossin'ed. The ilia, moreover, are 

 attached to the sacrum, which was in place in the skeleton. 

 The ilia have the same general form as in Megalosaurus. The 

 ischia are comparatively slender. They project well backward, 

 and for the last half of their length the two are in close appo- 

 sition. Their distal ends are coossified and expanded, as shown 

 in Plate VII. 



